Control system for billet cutting machines



Dec. 18, 1951 J. L. BIACH CONTROL SYSTEM FOR BILLET CUTTING MACHINESFiled July 21, 1948 5 Sheets- Sheet l 5 5 5 '5 6 6 b lmv 2 m 2 3 b H 321d 3. 2 0 I 0 "d 0 I L in M #32 L 1 no" 1 8 1 1| 8 M m fl/f .M 1 )111\/.QI-1 1 Q a 0 I a: 3 H V F r 3 2 5 i g m 6 1 4 V 2 0 1 n r fie 1 EE. n u 1i H]. m W 6 6 n 1 1 I: 7 7 7 7 I 1.: \ill INVENTOR JOHN L. BIACHATTOR N EYS 1951 .1. L. BIACH 2,578,778

CONTROL SYSTEM FOR BILLET CUTTING MACHINES Filed July 21, 1948 5Sheets-Sheet 2 Fig.2

INVENTOR JOHN L. BIACH ATTORNEYS Dec. 18, 1951 J. L. BIACH 2,578,778

CONTROL SYSTEM FOR BILLET CUTTING MACHINES Filed July 21, 1948 5Sheets-Sheet 5 INVENTOR JOHN L. BIACH BY MM/dM/lgz M ATTORNEYS PatenteclDec. 18, 1951 CONTROL SYSTEM FOR BILLET CUTTING MACHINES John L. Biach,Cranford, N. 1., aslignor to Air Reduction Company, Incorporated, acorporation of New York Application July 21, 1948, Serial No. 39,930

18 Claims. 1

This invention relates to machines for the multiple cutting of billetswith gas torches, and especially to the automatic control of themovement of the torches.

Various machines have heretofore been proposed for cutting into shortlengths, billets or other elongated pieces of metal of generally uniformcross-section. For reasons well understood in the art it has frequentlybeen desirable to employ cutters of the gas torch variety, but becauseof certain inherent characteristics of gas torches it has heretoforeproved difilcult, if not impossible, to control such torches so that theentire cutting operation is automatic. One condition which hasheretofore greatly interfered with the success of the automatic controlhas been that, although the billet or length of work to be out has beenof generally uniform cross-section, the piece has not been straight,viz., it has been warped or bent. As a result, if the gang of torchesspaced apart in accordance with the short lengths to be out are advancedas a unit toward the billet, certain torches will reach the edge of thebillet before other torches. In such case the proper instants forstarting the preheating flame and then the cutting flame would differwith different torches. Heretofore, the problem resulting from thisvariable condition has not been met satisfactorily in the automaticcontrol of multiple cutting torches.

In accordance with the present invention it is possible to cut a billetinto any desired number of shorter lengths automatically, even thoughthe billet is considerably warped or bent. As soon as the operation ofthe machine is begun, all of the cutting torches advance toward the edgeof the billet and each torch individually comes to rest at the startingpoint where the preheating is to commence, and waits there until all ofthe remaining torches have advanced to their respective preheatingpositions. As soon as the last torch reaches its starting position, allof the torches are caused simultaneously to preheat the work. If nopreheating is required the torches may commence the cutting operationimmediately after the last torch is in starting position. Thereafter themaster control circuit is actuated to move the torches through theircutting paths, following the contour of the billet, the speed at whichthe torches advance along their cutting paths being automaticallycontrolled.

When the cuts are all completed, and the gases are cut off, the torchesmove upward or away from the billets so as to clear the same and arereturned to their original starting positions ready 2 to respond to arepetition of the cycle as soon as a fresh billet is placed in cuttingposition.

A better understanding of the invention and the manner in which itoperates can best be had from the following description considered inconnection with the accompanying drawings, in which: I

Fig. 1 is a plan view of a simplified cutting machine in accordance withthe invention showing a portion of its length;

Fig. 2 is an elevational view partly in section through line 2-2 of Fig.1:

Fig. 3 is an electrical wiring diagram of the control connections forone torch with the apparatus in its inactive or at rest position; and

Fig. 4 comprises schematic diagrams of acrossthe-line or functioncircuits segregated from the complete circuit of Fig. 1; indicating alsoa repetition of elements for the control of additional torches, andfunction" circuits for automatic control of the gases.

The mechanism in accordance with the invention is illustrated in Figs. 1and 2 which show it in plan and elevational views, respectively. Thecutting torches III are of the type commonly used in torch cuttingmachines and are provided with the usual hose connections [3, l4 and iifor delivering thereto the necessary gases. The preheating gasescomprising oxygen and acetylene are provided separately through twohoses l3 and M (Fig. 2) and the cutting gas, such as commercially pureoxygen, is delivered through hose 15. The control of the supply of thesegases may be eilected manually but it is preferred to achieve suchcontrol by means of valves automatically responsive to the controlcircuits later to be described. Such valves, which may be e1ectricallycontrolled, are known in the art and form no part of the presentinvention. However, one manner in which the operation of such valves canbe controlled in response to the control system of the presentinvention, is described hereinafter. In Fig. 1, five cutting torches areshown by way of example, but it will be understood that any number oftorches, either more or less, may be controlled by the system of theinvention.

ported as on rollers ll which are mounted on a frame-work it of sturdyand rigid construction.

If desired, the uprights on which the rollers are supported may be madeto be adjustable lengthwise of the work-piece to permit greaterflexibility of support with respect to the spacing of the cuttingtorches. Any suitable type of workpiece support may be used dependingupon the nature and shape of the piece to be cut.

Each torch in is supported by a torch carriage 2 which moves the torchvertically and horizontally. The top of vertical column I8 is secured toa plate H, and the bottom of column I3 is supported by a foot flange 19.The slide piece 20, through which column l8 passes, is arranged to beslid vertically on the column by means of a lead screw 2| which isthreaded in a hole in piece 20. The upper end of screw 2| is journalledin plate II, and the lower end thereof is rotated by a reversibleelectric motor 22 which in turn is secured to the foot flange I9.

An extension of slide piece 29 forms a bracket 8 to which is attached ahorizontal column 23. At the end of column 23 is attached an end-plate 1corresponding to plate II on the vertical column. As before, theend-plate supportsone end of a lead screw 25 which is rotated by areversible electric motor 26, which in turn is secured to the bracket 8so that the lead screw 25 is parallel to the column 23. Sliding oncolumn 231s a slide piece 24 in which lead screw 25 is threaded, so thatrotation of this screw in either direction causes piece 24 to slidehorizontally in either direction. The cutting torch I is mounted inpiece 24 so as to be vertically adjustable therein.

Slide pieces 20 and 24 carry adjustable arms 2! and 28 on which aremounted photo-electric cells 29 and 30, respectively. Thesephoto-electric cells are arranged with suitable shields or lenses, orboth, so as to be sensitive only to light rays projected to them indefinite limited directions. Thus, photo-cell 29 receives only a narrowbeam of light reaching it in a horizontal direction, as represented bydash-dot line 31a, and similarly, photo-cell 30 is sensitive only to anarrow beam of light received in a vertical direction, as represented bydash-dot line 3|. These two lines are here represented as being marginalor tangential lines to the piece 9. Thus, if the work-piece gives oillight rays because of its high temperature, for example, the photo-cellwill respond when the cell moves with respect to the work from a linejust tangent to the work to a parallel line which does not pass throughthe work, and vice verse. I! the work is not at a temperature suchas toemanate radiations to which the photo-cells are sensitive, the sameresult may be achieved by placing behind the work suitable sources oflight, preferably polarized, and arranged so that the work casts ashadow along each of lines ilo and 3|.

Motor 22, in addition to driving screw 2| also drives apotentiometer 35coupled thereto by an electrically controlled clutch 36. A so-calledmagnetic clutch would be suitable. Motor 29 is similarly arranged todrive another potentiometer 33 through electrically controlled clutch34. The drives for these two potentiometers are so geared as to causethe potentiometers to extend to their full range when the slide pieces20 and 24 are at their lowest and outermost positions, respectiveb.Motor 26 is also coupled to a small elec-- tric generator 31 of suchnature that the output voltage is proportional to its speed.

A limit switch 38 is adjustably positioned on bracket 8 so as to beactuatedby striker on slide piece 24 at any desired extreme inwardposition of the piece resulting from the longitudinal adjustment ofswitch 38. A similar limit switch be actuated by striker 5 attached toslide piece 23. By longitudinal adjustment of switch 39 on the columniii the uppermost point in the travel of slide piece 20 may bepredetermined. The apparatus above described is all supported on aplatform 3 which may be arranged to form the top of a'chamber 50. Eachtorch carriage 2 may be adjusted longitudinally of the work-piece 3 bysliding the foot flange along rail I2 which is secured to platform 3.Thus, the lengths into which the work-piece is out can be predeterminedby the spacing of the foot flanges.

Within chamber it is located a master control mechanism where it isenclosed for protection against slag particles and dirt. It is, however,not necessary that this master control mechanism be located in the baseof the cutting apparatus because it may be located at any convenientplace inasmuch as it is connected to the apparatus only electrically.This mechanism controls all of the torches during the cutting operationand is actuated when, and not until, the last of the individual torcheshas been moved to its starting point. The mechanism is operated by areversible master motor 42 (Fig. 2) which translates a carriage 43 alonga slide bar 44 by rotating a lead screw 45. An arm 46 secured tocarriage 43 carries at the lower end thereof a sliding contact on apotentiometer 41. The carriage 43, in addition, carries cams 48 and 49which cooperate with cam followers 50 and 5|, respectively, tomove thesliders on potentiometers 52 and 53, respectively. The cams areremovable and are correlated as to shape and size with the shape, sizeand other characteristics of the workpiece to be cut. Cam 48, whichcontrols the vertical movement of the torch, may be of the same orsimilar shape as the work-piece, and cam 49 is shaped so that theparticular billet will be out according to the horizontal cutting speedsrequired. For convenience in illustration, the carriage 43 is shown inthe center of its travel path, whereas the torch III is shown at thebeginning of its travel path. Actually, with the cams at the positionsshown, the torch tip would normally be directly over the center of thework.

To the motor 42 is coupled an electric generator 54 of a type such thatthe output voltage 0! the generator is proportional to the motor speed.Strikers 4 and 4a are attached to carriage 43 in such a position as toactuate limit switches 55 and 56. At the ends of the travel of thiscarriage, switches 55 and 56 may be adjusted longitudinally, viz., inthe direction of movement of the carriage so as to be actuated at anydesired limit point of movement.

Operation The operation of the control system in accordance with theinvention will be described in connection with the circuit diagrams.Fig. 3 is a complete circuit diagram of a control system for one torchand includes the circuit elements and their connections. However, theoperation of the system and the functions of the elements'will morereadily be understood by reference to Fig. 4 which comprises a series ofacross-the-line or functionfdiagrams, together corresponding to thediagram of Fig. 3. From these diagrams it will be noted. that thecircuits as shown are intended to be operated from a direct-currentsource. Those skilled in the art will, however, appreciate that at leastsome of the circuits 3! is adjustably mounted on column l9 so as to mayreadily be operated from alternating ourrent provided appropriate typeof equipment be substituted where required. Assuming, therefore, thatfor present purposes direct current is employed, the three drivingmotors herein referred to, may conveniently comprise split seriesreversible motors, and motors 22 and 26 should have slightly greateracceleration than motor 42.

In order to simplify the description of the operation of the inventionthe circuits elements in the diagrams have been designated by lettersand numbers in accordance with their functions. To this end, the letterH has been employed in connection with circuit elements employed incircuits operating to drive the torch along its horizontal path, and theletter V for circuit elements operating to drive the torch along itsvertical path. The letter M is used to designate elements in the mastercontrol circuit. The letter R designates a relay, and the letter Pdesignates a polarized relay. Thus relay No. 1 in the master controlcircuit is represented as RMI, and the first one of its contacts byRMI-l." Similarly a polarized relay connected in the circuit whichoperates the horizontal drive mechanism is designated as RHPI, andcontacts on that relay are designated by the same number followed by l,2, etc. A number prefixed to letters, as in IRHI, designates an elementidentified with a torch of that number, viz., here torch #l, indicatingthat there are as many more duplicate elements in duplicate circuits asthere are torches. In the diagrams of Fig. 4 elements and circuitconnections thereto enclosed with dotted lines would be duplicated foreach additional torch. The letter enclosed in a parenthesis followingthe designation of a circuit element, such as RMI-J (a) is a referenceto the diagram (a) in which that element appears.

The operation of the system of the invention will now be described inconnection with the function diagrams of Fig. 4. Assuming that themechanism is in its inactive position whereat all of the equipment isdeenergized, carriage 43 of the master control (Fig. 2) will be fullyretracted and striker do will be against limit switch 56 causing theswitch to be actuated. Likewise all individual torches will be fullyretracted back, viz., nearest the post i 8 and up, nearest plate II; andslide pieces 24 and 20 will be in position to open limit switches 38 and39. In this condition the control circuits for the electrically operatedgas valves will be open so that no gas flows. It may be further assumedthat the work-piece 9 is in place on the supporting rollers 11.

The automatic cycle of operations is initiated by pressing the startbutton I, Fig. 4(a) which completes a circuit through master relay RMI(Fig. 4a), which, as shown, is connected across the line in series withthe starting button I and normally closed contacts I of relay RMEnergization of relay RMI causes the closing of all of its contactsincluding contacts RMl-l (a) which provides an electric lock-in circuitfor that relay so that it remains energized after the button i isreleased. Actuation of relay RMI also closes the other contacts thereofwhich cause all the horizontal-drive motors to move the torches forwardand all the vertical-drive motors to move the torches down. This isachieved by closure of contacts RMI-2(1) which feeds power to theforward coils of all horizontal-drive motors, and by closure of contactsRMI-3 (f) which energize relay IRV3 through normally closed contactiRVl-Z, which in turn closes contacts IRVI-l (d) to energize the downcoils to the vertical-drive motor 22.

The horizontaland vertical-drive motors continue to operate until allthe torches are in their proper positions to start the cuts. The cuttingposition is also the preheating position, and it is, incidentally,substantially the position of the torch I0 with respect to thework-piece 9 illustrated in Fig. 2. Whether preheating is required, andif so the duration of the preheating period is, of course, a variabledepending on the nature, dimensions and temperature of the material. Itthe temperature of the work is as high as its ignition temperature nopreheating would be required, it merely being necessary, in order tostart the cut, to open the cutting oxygen valve. 0n the other hand, itis usually necessary to provide preheating, and this step is commencedat the mentioned position. Suitable control of the period of preheatingis provided, and may be either manual or automatic.

Energization of relay RMI also closes contacts RMI-4(0) which permitsthe closing of the circuits including the photo-electric cells throughnormally closed contacts lRHI-l and lRVI-l. If the billet is hot enoughto emit radiations to which the photo-cells are sensitive they willrespond when the slide pieces on which they are supported move so thatthe photo-cells first in tercept such radiations, as represented bylines 3| and 3|(a), Fig. 2. If the billet is not hot enough to emitactivating radiations a suitable source or sources of light may belocated beyond and beneath the billet, and by suitable optical, orother, means arranged to emit light beams tangential to the work-piece.In this event the dash-dot lines 3! and 3Ia would represent the marginalline between such light beams and the shadow of the work-piece. Controlapparatus responsive to photo-electric cells can in a manner well knownin the art be caused to respond in either sense desired, so that thecontrol circuit is actuated either when the photo-cell moves from anilluminated area into an unilluminated area, or vice versa.

Assuming that the billet is of sufficiently high temperature to emitlight radiations, the photoelectric cells will be activated as soon asthey intercept the light rays on lines 31a, 3!. Activation of thesecells is correlated with a desired torch position by suitable adjustmentof arms 21 and 28. When the preselected position is reached by eachphoto-electric cell, the light from the billet shining into the cellsreduces their resistance permitting current to flow through them toenergize relays IR.V|(c) and IRHI. Actuation of these relays is notlikely to occur at the same instance because the amount of time requiredby each torch to reach its proper vertical position is likely to differfrom that taken to reach its proper horizontal position. However, aseach cell in turn is energized the respective relay is actuated to stopmovement of the horizontalor vertical-drive motor as the case may be,and when both motors have stopped, the torch will be in the preselectedpreheating or cutting position.

Actuation of relays IRVHc) and IRHI when photo-cells 29 and 30 havebecome conducting, closes contacts lRVl-l and |RH|-|, respectively, tolock in the corresponding relays, after the photo-cells have becomedeenergized. Relays IRHI and IRVI are so constructed that the lowercontacts (as shown in the drawing) close before the upper, normallyclosed contacts, open. 81-- multaneously, contacts iRVi-IG) and mm- 2(i)are reversed, thus respectively interrupting current through relayiRV3(f) to deenergize the downward driving coils of the vertical-drivemotor, and to deenergize the forward driving coils of thehorizontal-drive motor. Electric control clutches 34(b) and 36 whichare, respectively, connected in parallel with relays iRHI and IRVi,clutch potentiometers 33 and 35, respectively, Figs. 2 and 3, to thehorizontaland vertical-drive motors 26 and 22.

The actual preheating or the cutting cannot proceed until all of thetorches have been properly positioned, both horizontally and vertically.

'When each torch is in place to start its out (viz.,

at its starting point), relays iRHi(c) and lRVi are actuated to closecontacts iRHl--3(b) and lRVI-3 which are connected in series with relayRMZ and also with normally closed contacts RM3-2. The broken line in thediagram of Fig. 4, b represents the connection in that series circuit ofthe RHI-3 and RVl-3 contacts of the corresponding relays of all of thetorches. Consequently this circuit cannot be completed until the RHI andRV! relays of all torches as controlled by the respective photo-electriccells, have been actuated, in other words, until all torches are instarting position. Thus, when all the torches have arrived at theirrespective starting points the master relay RMZ is energized.

Actuation of relay RMZ closes contacts RM2- 2(b) which locks in" all ofthe series contacts RHI3 and RVi-3 through the shunt circuit,

- shown, and places all of the motor driving circuits in responsivecondition to move in paths determined by the master control, as will beexplained.

Actuation of relay RM2(b) closes contact RM2-i(h) completing the circuitthrough potentiometer 53 from which the tapped voltage determines thehorizontal speed control. This speed will at all times be proportionalto the potentiometer tap voltage as will later be described, and,therefore, is correlated with the cam 49 (Fig. 2) by means of which theposition of the potentiometer slider is determined. Energization ofpotentiometer 53 by closure of contacts RM2- i, in turn, energizes thecoils of the sensitive master relay RM(h) which closes RM5l(g) and thusenergizes the forward driving coils of master motor 42 (see also Fig. 2)through the contact RM2-4 which has already been closed by actuation ofrelay RM2. This relay operation results in driving motor 42 forward.Simultaneously, parallel circuits also supplied through potentiometer 53energize the relay IRH2 permitting a, circuit to be completed throughclosed contacts RM2-5(i), lRH2-i and iRHl-2 which energizes the forwarddriving coils of the horizontal-drive motor 26 causing it to move itstorch forward. Corresponding relays and contacts duplicated in the otherhorizontal-drive motor circuits cause similar movement of all of theother torches.

The actuation of relay IRVZU) or of IRV3 to energize the vertical-drivemotor and consequently to drive the torch carriage respectively pendentupcn the shape of c 48 as will later be described in more detail.

As the master motor '32 increases its speed it drives its coupledgenerator $601.) which generates a rising voltage of polarity oppositeto that across potentiometer 53. A speed will be reached at which thegenerated voltage equals the tapped potentiometer voltage at which pointthe relay RM5(h) will drop out because no current will pass through it.Since the current to the master motor 42 is supplied through contactsRM5i (g) of relay RME. the opening of these contacts causes the motor toslow down until the generator voltage drops sufficiently to permit relayRMS to pull in again. A balance point will, therefore, be reached whenrelay RME flutters in and out, just maintaining the proper motor speed.Therefore, the contacts RMd-i of relay RME may be considered ascontrolling the speed of the master motor. For convenience, this circuitin which relay RM5 is connected may be called a balance circuit. Thisrelay and generator 645 thus together function as a governorautomatically allowing motor 52 to operate at speeds corresponding tothe voltages tapped oif potentiometer 53 by its slider. As the mastermotor moves its carriage 43 (Fig. 2), the cam follower 5i willautomatically readjust the setting of potentiometer 53 in accordancewith the shape of cam 49, and consequently the speed of the master motorwill follow these automatic adjustments. Since cam 49 is shaped for theparticular billet that is being cut, the master motor will move athorizontal cutting speeds which are predetermined for the variousvertical dimensions of the work-piece. Y

The horizontal-drive motor is coupled to and drives its own generator310:.) which is connected in a circuit similar to that of the mastermotor generator 54. As shown in the diagram (Fig. 4, h) generator 31 isconnected in series with relay IRH2 so that the output voltage of thegenerator 31 is also compared with the tapped voltage from potentiometer53. Thus each torch-driving motor will operate at a speed correspondingto that of the master motor, and all motors will follow the speedpattern established up or down, is dependent, once the torch is in 1 inthe. master control system. Although the speeds of the horizontal-drivemotors and the master motor will be closely matched they will notcoincide. One or the other will be slightly greater causing the motorsgradually to become out of step and the torches to assume incorrectpositions, tending to result in a loss of the out. A supervisory orposition control is, therefore, provided which efiectively makes acontinuous check on the position of each torch and causes it to move infixed relation to the master control carriage, and, therefore, to movein the same speed pattern. This result is achieved by increasing ordecreasing the speed of any errant motor until the torch has regainedits proper relation to the master control position. Although speedchanges of almost any degree are possible in accordance with thisinvention, it is preferable to design the components so that the changeof speed of any given motor will not exceed approximately 10%.

The supervisory or position control just referred to includes thepotentiometer 41 (Fig. 2, Fig. 4, d) of which the slider alwaysindicates the position of the cam-supporting carriage 43, and thepotentiometer 33 of which indicates the horizontal position of the torch10. Since all horizontal-drive motor potentiometers were clutched totheir respective motors when the proper starting point was reached, via,when the photo-cell 30 etc., (Fig. 4, were energized, each potentiometer33 assumes a position corresponding to that of the slider 46 on masterpotentiometer 41. If the motor speeds matched exactly, the sliders onpotentiometer 33 and master potentiometer 41 would always be in the samerelative positions and in balanced relation. However, when the motorsget out of step and the cutting torch consequently out of position, thebalance between these potentiometers is upset. For instance when thehorizontal-drive motor 26 (Fig. 2) is running slightlytoo fast, theupset of the potentiometer balance energizes polarized relay IRHPU)which shifts its contact lRI-IPi from neutral position to the uppercontact so as to energize relay IRH3. This relay closes contact iRH3l(h)shunting relay IRHZ through resistance R1. At other times when therelative horizontal position of a torch lags that of the mastercarriage, relay i RHPQi) moves its contacts lRHP-l to the lowerposition, actuating relay IRHl which in turn closes contact IRHl-Hh),shunting generator 31 through resistance R2. The application of theshunt resistances R1 and R2 in this manner controls the relation betweenthe horizontal positions of the torch and the master control carriage 43as follows:

As above stated, the horizontal-drive motors, of which motor 25 is one,are calibrated for a slightly greater acceleration than the master motor42. During normal operation of the torch driving motors, thepotentiometer 53(h) provides a voltage which actuates relay IRH2 andpermits power tobe supplied to the motor driving coils through contactiRHZ-i (i). The connected generator 31 provides a voltage in oppositionto the potential tapped from the potentiometer 53 which, when the motorsare rumiing, creates a differential voltage in each circuit that doesnot affect the relay IRHZ as long as this differential exceeds apredetermined minimum. The motor 26 moves the torch forward at aslightly greater acceleration than that of the master motor, until thepositions of-the torch and the master motor carriage are out ofsynchronism, and consequently the differential between the voltagestapped from potentiometers33(;i) and 41 is of sufiicient magnitude toactuate relay IRHP which interconnects the sliders of those twopotentiometers. Each torch control circuit is independent oi the othersand responds only when its torch is out of position with the mastercontrol.

' As above described, relay contacts IRHP| (7) which actuate relay IRH3when the torch position leads that of the master carriage, connectsresistance R1 (h) in shunt with relay IRH2 by closure of relay contactIRH3-i. The shunting of resistance R1 across relay IRH2 reduces thevoltage across that relay to a value below the necessary minimumenergizing voltage, causing the relay to drop out and open its contactsiRH2-l (i). Forward acceleration of the corresponding motor 26 isthereby temporarily stopped. Acceleration is resumed when the torch hassubsequently fallen behind the carriage position during the idlinginterval, resulting in a reversed relative potential of potentiometers33 and 41 causing the relay IRHPU) to swing its moving contact iRHPI tothe lower fixed contact where it completes a circuit through relay lRHl.The resistance R: shunted across generator 31 by closure of contactsIRH4i(h) decreases the output voltage of the generator to a valuecorresponding to a speed lower than the actual speed of the generator,this decreased voltage being sufficiently small to create a potentialacross relay IRH2 to close contacts iRHl-Hi) and re-energize the forwarddrive coils of motor 26. As the motor has a slightly greateracceleration its torch will rapidly catch up with the master carriage,causing relay IRHP to be returned to its neutral position andsubsequently to its upper position, again completing the circuit throughrelay IRH3 as the torch position once more leads that of the mastercarriage.

The cycle just described is repeated in this and th other of the torchcontrol circuits to maintain a fine degree of position control by virtueoi the rapidity of .the cycle of operations which permits the torches tolead or lag the position of the master carriage 43 by but a minuteamount. Each torch continuously varies its position by this minuteamount either side of the exact corresponding position of the mastercarriage, but never gets out of position by any greater amount. In thismanner the control circuits act as a governor maintaining the position01' each 01 the torches in proper relation to the master carriage, andpermitting all of the torches to follow the pattern of cutting speed inaccordance with the contour of cam 49. While the horizontaldrive motorshave constant speed variation the change of speed is never great. Thesemotors are so controlled that they do not stop, nor are they driven athigh speed, because abrupt changes of speed are undesirable if thecutting operation is to be satisfactorily maintained.

Similarly, the vertical movement of the torches is also correlated withthe displacement of the master carriage. As has previously been shown,the vertical control of each torch includes a camactuated potentiometerbridge circuit such as is shown in diagrams Fig. 4(e) and (1) together.Upward or downward movement of the torches depends on the polarity ofthe potential impressed across the relay lRVP(e), which in turn isdependent on the comparative settings of the potentiometers 52 and 35.The speeds at which the torches move in either direction are generallyfaster than the movement of the master speed control mechanism. Thetorch position will therefore tend to be in advance of the controlmechanism positions and will, by the action of the control circuits, beretarded to follow a series of controlled vertical positions whichcorrespond to simultaneous horizontal displacements and thereiore to theshape of the work-piece. The polarized relay lRVP(e), when actuated soas to close the upper contact iRVPl(f), in turn actuates relay I RVZ(f), or when actuated to close the lower contact lRVP-i, actuates relayiRV3. Depending on the direction in which the connection betweenpotentiometers 52 and 35 is unbalanced, relay IRV2 closes contacts IRV2I(d) to energize the upward'driving coils of the motor 22, or relay IRV3closes contacts |RV3i(d) to energize the downward driving coils of thesame motor. Of course, only one set of motor driving coils can beenergized at a time because relay contacts IRVP-l are closed either upor down.

The setting of potentiometer 52 is determined by the position of cam 48and therefore by the position of the master control carriage. Thesetting of potentiometer 35 is determined by the actual verticaldisplacement of the torch as translated into the displacem t ofpotentiometer 35 through electric clutch 3 (c). This clutch couples thepotentiometer 35 to the torch carriage at the beginning of the cuttingcycle so that the potentiometer voltage indicates the actual 11,vertical displacement of the torch for all its positions duringthecutting cycle.

The to'flih is' caused to move upward at the beginning of a cuttingoperation when cam 46 elevates cam follower 50, together with itspotentiometer contact arm, to impress an initial differential voltageacross the relay lRVP(e). With the polarity in this ,direction, contactIRVP-Hf) energizes relay IRV2 which energizes the upward driving coilsof the motor 22 through the contacts lRV2-l(d). The torch carriage isthus driven upwardly at a rate cor- 12 disconnects the speed controlphase of the torch control. Simultaneously, contacts EMS-3(a) arereversed, opening the upper contact and responding to the speed of thedriving motor until its position gets ahead of the correspondingposition of the master control carriage. In

reaching this position the potentiometer 35 will have "matched"potentiometer 52, so that no current will flow through IRVP. Upwardacceleration of the torch carriage is therefore stopped until furtherdisplacement of cam 48 and readjustment of potentiometer 52reestablishes a sufllcient potential across IBVP to actuate it,whereupon the driving co of the motor will again be energized. The ac aloperational sequence of these torch circuits, being extremely rapid,causes the torch to follow a predetermined pattern of upward verticalmovement as indicated or determined by the shape of cam 46.

Downward motion of'the torch takes place when the cam follower isdisplaced in the opposite direction to that which'causes upward motion.A reversed polarity having been established across relay IRVP(e) thedownward driving coils of motor 22 become energized through contactslRVi-Hd) of relay IRVSU). Here again, the torch will tend to lead thecam position and will be held in check by the intermittent operation ofthe motor imposed by the balance requirements of the control circuit. Itshould be noted that as long as follower 50 of cam 46 is made to move inthe-same direction. the potential established across relay IRVP will bein the same direction, because uninterrupted movement of the-torchcarriage 2 is prevented when the potential across IRVP is zero or in anyevent less than that required to operate that relay. Subsequent movementof the cam follower will always reestablish the relay-actuatingpotential according to the direction in which the cam follower has beendisplaced. It should also be noted that all of the "vertical controlcircuits are so connected as to permit them to act independently of oneanother, each functioning as its corresponding torch position warrants.For this purpose contacts lRVl-4(j) are inserted in each circuit betweencontacts iRVP-l and the remaining parallel circuit connectionsassociated with the other motors. Contacts lRVl-4 are normally closed,but are opened during the cutting operation when the photoelectric cell26 has been energized and the relay IRVI has been actuated. Actuation ofrelay IRVP to close the upper one of the contacts lRVP-Hf) so as toenergize relay IRV2 does not result in energizing all such relays in theremaining motor circuits because of the open circuit at contactsIRVI4(!).

- When the end of the cutting cycle is reached, the striker 4 (Fig. 2)on carriage 43 closes limit switch 55. This energizes a master relayRM3(a) which is locked in by contacts HMS-4 connected across switch 55.Relay RM2(b) which is deenergized by the opening of the normally closedcontact EMS- 2, opens the circuit of potentiometer 530i) throughcontacts RM2-l and thus .closing the lower contact, as shown in thedrawing, reversing the connections to the master motor 42 and connectingthe coils for reversed operation. The master motor then drives carriage43 rapidly back to its inactive position at which striker 4a on carriage43 actuates switch 56, closing contacts 56-2(g) and opening contacts 56l(o) and holding them open until they automatically close again when thecarriage is next moved forward. The opening of contacts 56-! opens thereverse drive circuit of the master motor 42. The controls for theverticaland horizontal-drive motor circuits remain in circuit becausecontacts RM34(e) and EMS-411(1) connected in parallel with contactsRM2-3 and RM2-3a, respectively, which are now open, close to continueoperation of these circuits. When the follower 50 of cam 48 isretracted, the potential across relay IRVP is reversed, causing thecontacts of that relay to reverse thus energizing relay IRV2; andclosingcontact lRV2-l(d), which causes motor 22 to operate in high reversespeed corresponding to the speed of the master motor, driving the torchcarriage to its uppermost or inactive position. Upward vertical movementof the torch carriage is stopped when the slide piece 20 contactsadjustable limit switch 39 (Fig. 4, f and Fig. 2) which opens thecircuit to the upward driving coils of motor 22 by deenergizing relayIRV2(f).

The retum" coils of the horizontal-drive motor 26 are energized throughthe closing of contacts RM35(g), as above described, and lRH3-2.Whenever the torch lags behind the position of the carriage 43, aspreviously mentioned, the resulting unbalance between potentiometers 41and 33 energizes relay IRHP so as to operate relay IRH3(9') which thencloses contacts lRH3-2(i) connecting the return coils of motor 26 to theline. Motor 26 then drives the torch carriage horizontally back to thestarting point.

As each horizontal and vertical-drive motor operates to bring itsrespective torch back to the inactive position, the normallyvclosedcontacts IRV3-2(a), IRV-2 and iRH3-3 etc., will be closed after thepolarized relays of the control circuits (e) and (i) have been restoredto neutral position by return of the respective potentiometers to theirinitial positions. The completion of these contacts vin series withcontacts 56-2, which were closed by actuation of switch 56, establishesa circuit through the master. relay RM4 (a). Normally closed contactRM4-l (a) is thereby opened and all the master relays are deenergized.When relay RMI is deenergized electric clutches 34 and 36 (Fig. 4, c)are deenergized so as to uncouple potentiometers 33 and 35 from motors26 and 22, respectively. Contacts RMl--6(,f and RMl--5(i) are returnedto their normally closed positions as the master relay RMI isdeenergized. Under the conditions Just described all of the torches arein their most receded and uppermost positions, and the cycle commencingat this inactive position, passing through the starting point and thecutting operation and returning to the initial inactive position willhave been completed.

Gas control apparatus by which the preheating and cutting gases may beautomatically turned on and fed to the torches at the proper times maytake any of several forms. but may be as follows:

It maybe assumed that the preheating gas comprising oxygen and acetylenemay be controlled, respectively, by two electrically operated valves ofknown type, sometimes called "solenoid valves, and that the cutting gascomprising oxygen may be controlled by another electrically controlledvalve of similar type. These electrically operated valves arerepresented Ming; 4, k, I and m, and are actuated in response to theclosing of relay contacts.

If relay RM2 is furnished with a sixth pair of contacts connected acrossthe line in series with the oxygen (02) and acetylene (CzHz) valves, asshown in Fig. 4, k, the preheating gas will be automatically fed to thetorches as soon as the relay RM2 is actuated. It will be recalled thatrelay RM2 is actuated as soon as the last of the photo-electric cellshas been actuated, viz., when all of the torches have reached theirstarting points or positions. Inasmuch as a time delay is I frequentlyrequired to permit preheating before the torches begin to move on theircutting paths, the relay contacts RM2-l, in this case, instead of beingconnected in circuit to energize potentiometer 5301) would be omitted,and contacts RTD-l, of a suitable time-delay relay would be substitutedtherefor, as indicated in Fig. 4, h. Also, contacts RMZ-Mg) of relayRM2, instead of being connected to the forward moving coils of mastermotor '42 would be omitted, and contacts RTD-4 of the same time-delayrelay would be substituted therefor, as shown in Fig. 4, g. Thistime-delay relay should be of a type permitting the period of delay tobe adjustable, and it would be connected across the line by closure of aseventh pair of contacts RM2-1(l) of relay 3M2. Hence, when relaycontacts RMZ-l close, relay RTD will be energized, but the closing ofthe contacts of relay RTD will be delayed depending upon the time delayadjustment. Relay RTD carries seven sets of contacts, six of themreplacing, and having the same function as, those of relay RM2 asfollows: RDTI for RM2-l (h), EDT-2 for RM2,2(b), RTD-3 for RM2-3(e),

Mg) and RTD5 for RM2 -5(i). If this timedelay relay is initiallyadjusted for a time period equal to that required for preheating; theparticular work-piece to be cut, the cutting gas will likewise beautomatically controlled as follows:

When relay RM2 is energized as above mentioned, contacts RM2-|(l) willclose, energizing relay RTD. After expiration of the preselected delayperiod for which relay RTD has been set, contacts RTD-6(m) will close,opening the cutting-gas valve which is connected in series therewithacross the line. Contacts RTDl and RTD-2 also close upon operation ofrelay RTD and in so doing initiate operation of the master motor 42 andat the same time energize the master motor control circuit of Fig. 4, h,thus automatically initiating the cutting movement of the varioustorches simultaneously with the application of cutting gas to theworkpiece. The remaining contacts of rela RTD have the same functions'asthe corresponding contacts of relay RMZ. If necessary, a suitablecontrol may be provided to discontinue the preheating gas after thecutting gas has been ignited, but ordinarily this would not be requiredbecause it is customary not to cut off the preheating gas during thecutting operation. At the end of the cutting cycle, as previouslyexplained, the relay RM2 is deenergized by the opening of relay contactsEMS-2 which occurs upon actuation of limit switch 55 when master controlcarriage 43 reaches the end of its travel. By this means all of thegases are automatically cut off by the closing of the gas control valveswhen the relay RM2 is deenergized.

What is claimed is:

1. In combination with a billet cutting machine including a plurality ofsupporting standards, cutting torches supported by torch-carriagesmovable on said standards vertically and horizontally, drive means formoving said carriages in each of said directions, unitary control meansactuating all of, said drive means simultaneously and billet supportmeans for holding a billet in cutting relation to said torches, anautomatic control system which includes photoelectric cells movable withsaid carriages and arranged so that one cell receives light from saidbillet only in a vertical direction and another cell receives light fromsaid billet only in horizontal direction, control circuits actuated inresponse to said photoelectric cells for automatically stopping themovement of each torch-carriage when the tip of its torch arrives at apreselected position with, respect to said billet, and control meanscausing automatic resumption of movement of all of said torches afterthe last thereof has arrived at its said preselected position.

2. A control system according to claim 1, in which said control includesa master circuit in which there are connected a plurality of separatecircuit elements actuated respectively in response to said photoelectriccells, a master element connected in said master circuit which isactuated only as a result of the actuation of all of said circuitelements, and connections for energizing all of said drive means uponactuation of said master element.

3. A system according to claim 2 wherein said master element comprises atime delay device arranged to effect energization of said drive means ata predetermined time after said master element is actuated.

4. In an automatic billet cutting machine adapted to operate in acutting cycle, a cutting torch supported on a carriage movablevertically and horizontally, vertical-drive and horizontaldrive meansfor said carriage, first and second potentiometers having slidersmechanically coupled to each of said drive means, respectively, a mastercontrol circuit for controlling operation of both said drive means, saidmaster control circuit including third and fourth potentiometerselectrically connected, respectively, to said first and secondpotentiometers to form two balance circuits, and a control elementconnected in each balance circuit to control the operation of each ofsaid drive means, separately in response to the balance between saidpotentiometers in each of said balance circuits.

5. In a machine according to claim 4, a clutch serving to couple anduncouple each of said drive means to and from the potentiometerassociated therewith, and means automatically actuating said clutches atthe beginning and end of the cutting cycle.

6. In an automatic billet cutting machine adapted to operate in acutting cycle, a cutting torch supported on a carriage movablevertically and horizontally, vertical-drive and horizontal drive meansfor said carriage, a master control circuit, a drive-control circuit foreach of said drive means, two balance circuits each including a mastercircuit control element and a drive circuit control element, a polarizedcontrol element connected in each balance circuit, and connections fromeach polarized control element to control the operation of one of saiddrive means.

7. In a cutting machine suitable for automatically cutting a bent billetinto a plurality of shorter lengths, a plurality of cutting torches eachsupported on a separate movable torch carriage, drive means for each ofsaid carriages, a support for holding a billet in cutting relation tosaid torches, control means actuating all of said drive meanssimultaneously to move each torch individually into a predeterminedcutting position uniformly spaced from the billet irrespective of itscontour at the point where such torch is to start its cut, means forautomatically stopping each carriage when the torch which it supportsarrives at said position, and means for initiating cutting movement ofall of the torch carriages simultaneously after all of said torches havereached said predetermined cutting positions.

8. A cutting machines according to claim 7 wherein said last mentionedmeans includes a master control system coupled to said control means soas to effectively control the speed of said drive means, said drivemeans including horizontal and vertical drive means, and cam means insaid system shaped to predetermine the speeds of said horizontal andvertical drive means in accordance with the cross-sectional shape ofsaid billet.

9. In a cutting machine according to claim '7. a first control elementwhich is actuated only when all of said torches have arrived at theirrespective starting points, and a second control element actuated bysaid first control element so as to start said torches on their cuttingpaths.

10. In a cutting machine for automatically,

cutting a billet, a cutting torch mounted on a movable carriage, a drivemotor for driving said carriage, a speed control circuit for said motor,and a master control system linked to said speed control circuit so asto control the speed of said drive motor, said master control systemincluding a master motor, a source of voltage generated in proportion tothe speed of said master motor, a master carriage driven by said mastermotor, a first cam element moved by said master carriage, apotentiometer having a fixed voltage connected thereacross, a second camelement mechanically coupled to move the slider 01 said potentiometer, abalance circuit including said source of voltage and the slider of saidpotentiometer and a control element, whereby the eflective voltageimpressed on said element is a function of the speed of said mastermotor and of the position of said cam, and connections from said controlelement to control the speed of said master motor.

11. In a cutting machine for automatically cutting a billet, a cuttingtorch mounted on a movable carriage, a drive motor for driving saidcarriage, a first potentiometer having a slider driven by said drivemotor in proportion to the displacement of said carriage, a speedcontrol circuit for said motor, a master control system including amaster motor, a master carriage driven by said motor and a masterpotentiometer having a slider moved by said carriage, a source ofefiectively fixed voltage connected across each of said potentiometers,a polarized control element connected in circuit between the sliders ofsaid potentiometers, and connections between said control element andsaid speed control cir- 16 cuit whereby to control the speed of saiddrive motor as a function of the relative positions of said carriages.

12. In acutting machine for automatically cutting a billet, a pluralityof cutting torches arranged to be drivn in individually different paths,a plurality of torch-'drivingmotors including a horizontal-drive motorand a verticaldrive motor operatively coupled to each torch to controlthe path and speed of movement of said torch, means for independentlycontrolling the horizontal-drive motors and the vertical-drive motors,respectively, a master motor, means actuated by said master motor forregulating the cutting speed of all said torch-driving motors inresponse to that of the master motor, a master control system includinga master control circuit for controlling the speed of said master motorand a mechanism having a speed pattern pre-= selected in accordance witha cross-sectional dimension of the billet, and connections from saidspeed pattern mechanism to said master motor control circuit'forautomatically controlling the speed of said master motor and hence therelative speeds of ,said horizontal driving motors and of saidverticaldriving motors, respectively, in accordance with said speedpattern.

13. A system for automatically controlling the position of a movingelement, including in combination, an electric motor coupled to saidelement for moving the same, a generator driven by said motor and havingan output voltage substantially proportional to the speed of said motor,a constant voltage source, a first potentiometer connected across saidvoltage source, a first balance circuit comprising said generator and afirst relay connected in series between the slider oi said firstpotentiometer and one side of said voltage source so that the voltagesof said generator and of said source are in opposition, second and thirdpotentiometers connected in parallel across said voltage source, asecond balance circuit comprising a polarized relay connected betweenthe sliders of said second and third potentiometers, second and thirdrelays, contacts on said polarized relay including two fixed contactsand a moving contact which is connected to one side of an electric powersource, said second and third relays being connected respectivelybetween said ,fixed contacts and the other side of said last mentionedpower source, first and second resistors, said second relay havingcontacts connecting said first resistor in shunt to said first relay,said third relay having contacts connectin said second resistor in shuntto said generator, coupling means coupling the slider of said secondpotentiometer and said element whereby the position of the slider ofsecond potentiometer is determined by the position of said element, andcontacts on said first relay operable upon closure to connect said motorto a power line.

14. In a system according to claim 13, a movable master position controlelement, and linking means interconnecting said master control elementand the slider of said third potentiometer whereby the position of theslider of said third potentiometer is determined by the position of saidmaster control element.

15. In a, system for automatically controlling the speed of an electricdriving motor operated from a power line, the combination whichincludes, a generator driven by said motor and having an output voltagesubstantially proportional to the speed of said motor, a source ofconstant voltage, a balance circuit including in series a first relayand said generator connected across said voltage source with the outputvoltage of said generator in opposition to that of said source withrespect to said relay, a master control circuit, second and third relaysactuated by said master control circuit, a resistor connectible byclosure of contacts of said second relay effectively to reduce thevoltage on said first relay, a second resistor connectible by closure ofa contact of said third relay effectively to reduce the voltage outputof said generator, and contacts on said first relay operable uponclosure to connect said motor to said line.

16. A system according to claim 15 in which said master control circuitincludes a master control motor, the normal rate of acceleration of saidmaster motor being less than that of said driving motor.

17. In combination with a billet cutting machine including a pluralityof supporting standards, cutting torches supported by torch-carriagesmovable on said standards vertically and horizontally, drive means formoving said carriages in each of said directions, unitary control meansactuating all of said drive means simultaneously and billet supportmeans for holding a billet in cutting relation to said torches, anautomatic control system which includes photo-electric cells movablewith said carriages and arranged so that one cell receives light fromsaid billet only in a vertical direction and another cell receives lightfrom said billet only in a horizontal direction, and control circuitsactuated in response to said photoelectric cells for automaticallystopping the movement of each torch-carriage when the tip of its torcharrives at a preselected position with respect to said billet.

18;. In a cutting machine suitable for automatically cutting a bentbillet into a plurality of 18 shorter lengths, a, plurality of cuttingtorches each supported on a separate movable torch carriageindependently controllable, a support for holding a billet in cuttingrelation to said torches, said carriages and torches being spaced apartlongitudinally of said support, drive means for each of said carriages,individual control means for independently controlling each of saiddrive means, unitary control means actuating all of said individualcontrol means simultaneously to move each torch individually into apredetermined cutting position uniformly spaced from the billetirrespective of its contour at the point where such torch is to startits cut, and means for automatically stoppin each carriage when thetorch which it supports arrives at said position.

JOHN L. BIACl I.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,021,196 Oldham Nov. 19, 19352,116,593 Bouvier et a1. May 10, 1938 2,143,969 Biggert, Jr Jan. 17,1939 2,177,276 Bucknam Oct. 24, 1939 2,229,448 Garman Jan. 21, 19412,269,643 Bechtle et a1 Jan. 13, 1942 2,277,054 Anderson Mar. 24, 19422,281,844 Jones May 5, 1942 2,404,600 Scovill, Jr a- July 23, 19462,504,171 Anderson Apr. 18, 1950 FOREIGN PATENTS Number Country Date84,276 Sweden Sept. 11, 1935

